16.16: Medium span steel‐concrete composite bridges: plate girders or box girders

Abstract

In today's environment and client's requirements, solutions for medium span road and rail bridges within the UK tend to result in an overlap between three types of steel-concrete composite decks. From the ban and moratorium imposed on grouted post-tensioned concrete bridges since the early 1990s, braced pairs of plate girders, twin plate girders with cross girders (ladder-deck) as well as steel box sections have dominated the British construction market for spans varying between 30m and 70m. Open box sections (bath tub) are sometimes preferred due to specific geometry requirements or even purely from aesthetic requirements. This paper reviews and compares the options based on the available design guidelines as well as the author's recent experience in delivering detail designs of each alternative arrangement. The aim of this paper is to summarise the main driving factors leading to the choice of a specific arrangement. A discussion on geometrical considerations (skew, curve, span to depth slenderness ratios) as well as a comparison of estimated weight of steel per metre square of deck for each option are included. Each solution is presented from the detail design and fabrication point of views including the transport criteria, the erection consideration and the temporary stability stages. The aesthetic and the whole life cost aspects (such as durability, inspection and maintenance) are also considered in the comparison.